This invention relates to an apparatus and method for batch feeding sheets.
A high speed method of batch feeding sheets is to serially feed the sheets onto a table until the desired batch size has been accumulated, whereupon the table is rapidly retracted to drop the batch onto a downstream stack handler. The table is then rapidly extended again so that the process may be repeated. Such a table may be referred to as a reciprocating table. This type of batch feeding apparatus may have endless belt conveyors which sandwich the sheets and eject them toward the reciprocating table. A difficulty with this arrangement is that if the sheets are large and thin, they tend to buckle when ejected by the belt feeders and may cause jams. Furthermore, the front of some paper stock sheets are bruised when they impact the table or a front stop for the table. Also, feeding at high speed tends to cause small transverse misalignments in the sheets which stack at the table. It is difficult to steer sheets at high speeds in order to avoid such misalignments without causing buckling.
This invention seeks to overcome drawbacks of known reciprocating table batch feeders.
The subject invention places a shingling nip roll between an infeed conveyor and the reciprocating table. The nip roll slows the speed of the sheets thereby reducing bruising and buckling. Further, the trailing end of a dropped sheet is overlapped by a leading end of the next upstream sheet which assists in maintaining control of the dropped sheet as it drops onto the reciprocating table.
Accordingly, the present invention provides a batch sheet feeder, comprising: a sheet feeding conveyor operating at a first speed; a shingling nip roll spaced downstream of a downstream end of said sheet feeding conveyor, said nip roll operating at a second speed slower than said first speed; a sheet support extending between said downstream end of said sheet feeding conveyor and said nip roll; a horizontally reciprocating table downstream and below said nip roll.
In accordance with another aspect of the present invention, there is provided a batch feeding method comprising: feeding sheets travelling at a first speed through a nip roll travelling at a slower second speed such that said sheets are shingled; at a drop station, serially dropping sheets from said shingled sheets downwardly onto a reciprocating table such that a tail end of a dropped sheet is partially controlled by an overlapping leading end of a next upstream sheet.